Substantial technical effort has been directed to extend the storage time for foodstuffs and other microbiologically labile products and to preserve these products against microbiological spoilage. Such efforts have involved both the treatment of products and the development of packaging techniques for preservation.
The present invention addresses the particular need which exists for methods and apparatus for sterilizing or reducing the microbiological burden on the surfaces of or within foodstuffs and other products, which may be utilized to reduce or eliminate the need for chemical preservatives. For example, baked goods such as bread may accumulate microorganisms, such as mold spores, from the air after they are baked but before they cool sufficiently to be packaged. Any substantial reheating of the baked goods would excessively dry the products and new methods for surface sterilization of such foodstuffs would be desirable. Food products may also be subject to enzymatic degradation, which limits shelf life of the food product. Enzymatic degradation is particularly rapid and evident for example in the browning of freshly cut potatoes and apples, but has adverse effects in a great variety of foods, alone, or in combination with microbially caused deterioration. For example, foods such as fresh fish have a relatively limited storage time before being subject to microbial and/or enzymatic spoilage, which limits the distribution and marketing of fresh fish products. Methods and apparatus suitable for extending the shelf life of perishable foods such as fresh fish, poultry, beef and pork would be desirable.
Also, many products, for example some juices, are now processed through the use of heat under conditions which, in order to produce the desired reduction in biological activity, cause a degradation of the taste and palatability of the treated food product. Methods and apparatus for reducing or eliminating biological activity without such degradative heating would be desirable for providing taste and palatability benefits which would increase the consumer interest and hence market for products so treated.
Significant research and development effort has recently been directed to aseptic packaging technology for packaging of sterilized food products (including high and low acid foods) in sterile packaging materials, in order to provide preserved foodstuffs having an extended shelf life. However, such methods and apparatus may have various disadvantages such as requiring the extensive use of chemical disinfectants which may leave residual chemical products on the packaging material or foodstuff. New methods and apparatus for sterilizing food product packaging material and for aseptic packaging would be desirable.
The photobiological effects of light, including visible light (380-780 nm), near ultraviolet light (300-380 nm) and far ultraviolet light (190-300 nm), have been studied for many years, for example, as reported in Jagger, J., "Introduction to Research in Ultraviolet Photobiology", Prentice Hall, Inc., 1967, and efforts have been made to employ light to sterilize food products or containers for food products. U.S. Pat. No. 2,072,417 describes illuminating substances, e.g., milk, with active rays, such as UV rays. U.S. Pat. No. 3,817,703 describes sterilization of light-transmissive material using pulsed laser light. U.S. Pat. No. 3,941,670 describes a method of sterilizing materials, including foodstuffs, by exposing the material to laser illumination to inactivate microorganisms. However, such methods have various deficiencies, such as limited throughput capacity, limited effectiveness, adverse food effects, inefficient energy conversion (electrical to light) and economic disadvantages.
Accordingly, it is an object of the present invention to provide new methods and apparatus for the reduction of the biological burden of food products, liquids, equipment, devices and atmospheres. It is a further object to provide new methods and apparatus for preserving foodstuffs and for packaging of foodstuffs, particularly including improved aseptic packaging processes and apparatus.